docs: def all_branch_orders(h):
      """
      Produces a list branch orders for each section (following pre-order tree
      traversal)
      """
      #Iterate over all sections, find roots
      roots = []
      for section in h.allsec():
          sref = h.SectionRef(sec=section)
          # has_parent returns a float... cast to bool
          if sref.has_parent() < 0.9:
              roots.append(section)
  
      # Build list of all sections
      order_list = []
      for r in roots:
          add_pre(h,[],r,order_list,0)
      return order_list